Pre-synchronization Control Strategy for Grid Connection of GFM Converter Based on LADRC

The grid-forming (GFM) converter simulates the rotor characteristics of a synchronous motor through the application of the virtual synchronous generator control (VSG), providing crucial inertia and damping support for the grid connection of distributed generation (DG). However, in the island mode, when the DG is closed and connected to the grid, due to the existence of the non-synchronous grid connection phenomenon, a large inrush voltage will be generated. Aiming at this problem, this research introduces a pre-synchronization control strategy based on the principles of linear active disturbance rejection control (LADRC). Firstly, this paper introduces the pre-synchronization control strategy based on coordinate transformation and conducts a rigorous theoretical derivation of it. Secondly, the LADRC is designed and applied to the active power control loop. Meanwhile, the parameter selection principles of the LADRC controller are expounded. Finally, a pre-synchronization control model based on coordinate transformation and the LADRC is built on the MATLAB/Simulink. The results show that the control strategy proposed in this paper can significantly shorten the grid connection time of the DG, fully verifying the superiority of the proposed control strategy.